All tests should give some portion of data to the producer and use the rest.

tests/fuzz/block_round_trip.c

@@ -52,9 +52,13 @@ static size_t roundTripTest(void *result, size_t resultCapacity,
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
+    /* Give a random portion of src data to the producer, to use for
+    parameter generation. The rest will be used for (de)compression */
     FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
+    size_t producerSliceSize = FUZZ_dataProducer_uint32Range(producer, 0, size);
+    size = FUZZ_dataProducer_contract(producer, producerSliceSize);
+
     int cLevel = FUZZ_dataProducer_uint32(producer) % kMaxClevel;
-    size = FUZZ_dataProducer_remainingBytes(producer);
 
     size_t neededBufSize = size;
     if (size > ZSTD_BLOCKSIZE_MAX)

tests/fuzz/dictionary_decompress.c

@@ -24,7 +24,12 @@ static ZSTD_DCtx *dctx = NULL;
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
+    /* Give a random portion of src data to the producer, to use for
+    parameter generation. The rest will be used for (de)compression */
     FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
+    size_t producerSliceSize = FUZZ_dataProducer_uint32Range(producer, 0, size);
+    size = FUZZ_dataProducer_contract(producer, producerSliceSize);
+
     FUZZ_dict_t dict;
     ZSTD_DDict* ddict = NULL;
     int i;
@@ -43,8 +48,8 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
                 (ZSTD_dictLoadMethod_e)FUZZ_dataProducer_uint32Range(producer, 0, 1),
                 (ZSTD_dictContentType_e)FUZZ_dataProducer_uint32Range(producer, 0, 2)));
     }
-    /* Run it 10 times over 10 output sizes. Reuse the context and dict. */
-    for (i = 0; i < 10; ++i) {
+
+    {
         size_t const bufSize = FUZZ_dataProducer_uint32Range(producer, 0, 2 * size);
         void* rBuf = malloc(bufSize);
         FUZZ_ASSERT(rBuf);

tests/fuzz/dictionary_round_trip.c

@@ -68,13 +68,16 @@ static size_t roundTripTest(void *result, size_t resultCapacity,
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
+    /* Give a random portion of src data to the producer, to use for
+    parameter generation. The rest will be used for (de)compression */
+    FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
+    size_t producerSliceSize = FUZZ_dataProducer_uint32Range(producer, 0, size);
+    size = FUZZ_dataProducer_contract(producer, producerSliceSize);
+
     size_t const rBufSize = size;
     void* rBuf = malloc(rBufSize);
     size_t cBufSize = ZSTD_compressBound(size);
-    void* cBuf;
-
-    FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
-
+    void *cBuf;
     /* Half of the time fuzz with a 1 byte smaller output size.
      * This will still succeed because we force the checksum to be disabled,
      * giving us 4 bytes of overhead.

tests/fuzz/simple_compress.c

@@ -24,14 +24,17 @@ static ZSTD_CCtx *cctx = NULL;
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
+    /* Give a random portion of src data to the producer, to use for
+    parameter generation. The rest will be used for (de)compression */
     FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
+    size_t producerSliceSize = FUZZ_dataProducer_uint32Range(producer, 0, size);
+    size = FUZZ_dataProducer_contract(producer, producerSliceSize);
 
-    int const level = (int)FUZZ_dataProducer_uint32Range(
-                                producer, 0, 19 + 3) - 3; /* [-3, 19] */
     size_t const maxSize = ZSTD_compressBound(size);
     size_t const bufSize = FUZZ_dataProducer_uint32Range(producer, 0, maxSize);
 
-    size = FUZZ_dataProducer_remainingBytes(producer);
+    int const level = (int)FUZZ_dataProducer_uint32Range(
+      producer, 0, 19 + 3) - 3; /* [-3, 19] */
 
     if (!cctx) {
         cctx = ZSTD_createCCtx();

tests/fuzz/simple_decompress.c

@@ -23,7 +23,11 @@ static ZSTD_DCtx *dctx = NULL;
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
+    /* Give a random portion of src data to the producer, to use for
+    parameter generation. The rest will be used for (de)compression */
     FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
+    size_t producerSliceSize = FUZZ_dataProducer_uint32Range(producer, 0, size);
+    size = FUZZ_dataProducer_contract(producer, producerSliceSize);
 
     if (!dctx) {
         dctx = ZSTD_createDCtx();
@@ -34,10 +38,6 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
     void *rBuf = malloc(bufSize);
     FUZZ_ASSERT(rBuf);
 
-  /* Restrict to remaining data. If we run out of data while generating params,
-   we should still continue and let decompression happen on empty data. */
-   size = FUZZ_dataProducer_remainingBytes(producer);
-
     ZSTD_decompressDCtx(dctx, rBuf, bufSize, src, size);
     free(rBuf);
 

tests/fuzz/simple_round_trip.c

@@ -52,12 +52,19 @@ int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
     size_t cBufSize = ZSTD_compressBound(size);
     void* cBuf;
 
+    /* Give a random portion of src data to the producer, to use for
+    parameter generation. The rest will be used for (de)compression */
     FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
+    size_t producerSliceSize = FUZZ_dataProducer_uint32Range(producer, 0, size);
+    size = FUZZ_dataProducer_contract(producer, producerSliceSize);
+
     /* Half of the time fuzz with a 1 byte smaller output size.
      * This will still succeed because we don't use a dictionary, so the dictID
      * field is empty, giving us 4 bytes of overhead.
      */
     cBufSize -= FUZZ_dataProducer_uint32Range(producer, 0, 1);
+    size = FUZZ_dataProducer_remainingBytes(producer);
+
     cBuf = malloc(cBufSize);
 
     FUZZ_ASSERT(cBuf && rBuf);

tests/fuzz/stream_round_trip.c

@@ -125,15 +125,15 @@ static size_t compress(uint8_t *dst, size_t capacity,
 
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
-    size_t neededBufSize;
-    neededBufSize = ZSTD_compressBound(size) * 5;
-
     /* Give a random portion of src data to the producer, to use for
     parameter generation. The rest will be used for (de)compression */
     FUZZ_dataProducer_t *producer = FUZZ_dataProducer_create(src, size);
     size_t producerSliceSize = FUZZ_dataProducer_uint32Range(producer, 0, size);
     size = FUZZ_dataProducer_contract(producer, producerSliceSize);
 
+    size_t neededBufSize;
+    neededBufSize = ZSTD_compressBound(size) * 5;
+
     /* Allocate all buffers and contexts if not already allocated */
     if (neededBufSize > bufSize) {
         free(cBuf);

tests/fuzz/zstd_frame_info.c

@@ -21,10 +21,6 @@
 int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size)
 {
     ZSTD_frameHeader zfh;
-    /* Consume the seed to be compatible with the corpora of other decompression
-     * fuzzers.
-     */
-    FUZZ_seed(&src, &size);
     /* You can fuzz any helper functions here that are fast, and take zstd
      * compressed data as input. E.g. don't expect the input to be a dictionary,
      * so don't fuzz ZSTD_getDictID_fromDict().